![Sample our Environment & Agriculture journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5934/TOC-Subject-Sample-2021-Environment-Agriculture.jpg"})
Abstract
Three fresh and three dried diets comprising grasses and legumes were fed to six sheep, housed in metabolism crates, to determine the distribution of mineral elements between solids and supernatant fractions of rumen and abomasal digesta. Apparent absorption of elements from the rumen and intestine were also measured, together with dry matter (DM) digestibility. The feeds offered were fresh perennial ryegrass, fresh red clover, fresh lucerne, chaffed lucerne hay, chaffed meadow hay, and lucerne pellets. The feeds provided a 2-fold range in concentration of macro- and micro-elements in their DM (except for zinc (Zn)), with DM digestibilities from 54 to 78%. In rumen contents (pH 6.3–6.5) over 85% of calcium (Ca), manganese (Mn), copper (Cu), and zinc (Zn), and over 70% of magnesium (Mg), phosphorus (P), sulphur (S), and iron (Fe) were associated with the solid fraction (except for Mg and P with ryegrass). Potassium (K) and sodium (Na) predominated in the supernatant. In the abomasum (pH 2.4–2.9) less than 42% of Ca, Mg, P, Mn, and Zn were associated with solids. Only S, Fe, and Cu predominated in abomasal solids DM. Fresh feeds, as a group, were not substantially different to dried feeds with respect to either the distribution of elements between digesta fractions or the apparent absorption of elements from the digestive tract. The principal feed effect was the wide variation in the concentrations of elements in the DM, and not the distribution and absorption of individual elements. The change in concentration of elements between rumen and abomasal solids DM is indicative of an association through binding or adsorption rather than an incorporation into plant or microbial structure. The dissociation from solids in the abomasum has important implications for absorption from the intestine; however a rise in pH down the intestine is likely to reduce the solubility and availability of most elements for absorption.